The main components of automatic transmissions are conventional, as are manually operated gear mechanisms, wherein the shifting and/or starting clutch between the driving motor and transmission, as well as the selection and shifting of gears, are actuated automatically using corresponding operating elements. These operating elements are typically configured as hydraulic or pneumatic actuating cylinders or as electric actuators, which act upon actuating elements for the above gear functions. The actuating elements can be provided on or in the transmission.
For the actuation of hydraulic or pneumatic operating elements, pressure-generating and control devices are required which, according to the state of the art, comprise a hydraulic or pneumatic pump as the pressure-generating device, a pressure accumulator, a hydraulic or pneumatic control unit with control valves and sensors, which are connected to a central control and regulating device and can be actuated by the same, based on control and regulating functions stored there.
In variable speed gear wheel transmissions configured as constant-mesh countershaft transmissions, the torque-transmitting connection of two gear elements is established by clutch gearing. In the case of such constant-mesh countershaft transmissions, at least part of the running gears are permanently engaged and the spur gears are connected to the shafts by sliding sleeves, via claw-type involute splines, which are provided laterally on the spur gears. To facilitate shifting, the claws are supplemented with synchronization and locking synchronization devices. The synchronization devices provide rotational speed adjustment of two gear elements rotating at different speeds and of the parts connected thereto, so that they can be connected to each other without any grating noise. Known synchronization devices comprise locking devices, which are not released until the gear elements to be connected have synchronous speeds and allow the form-fit connection of the gear elements to be connected. Locking devices of this type prevent grating noise and damage to the form-fit shifting elements.
The disadvantage is that actuating elements, such as shifting rods or shifting forks, may bend to a certain degree due to the forces occurring during a gear shift, so that ultimately the position of the shifting fork located on the shifting fork base does not correspond to the precise position of the sliding sleeve. Due to the high stress applied on transmissions, which results in strain or bending of the transmission shafts, the shifting forks are frequently not in contact with the sliding sleeves across the entire circumference of the sliding sleeves thus allowing jamming between the shifting fork and sliding sleeve. This measure, however, lowers the rigidity of the shifting fork and thus increases the bending tendency of the shifting fork.
DE 103 36 971 B3 discloses an arrangement for determining the position of a gearshift fork or gear lever, according to which a precise displacement signal can be achieved for adjusting the sliding sleeve actuated by a gearshift fork. Due to the fact that a position transmitter is located basically at the end of the gearshift fork, possible deflections of the gearshift fork are compensated for so that a transmitter-sensor unit can precisely determine the position of the sliding sleeve provided on the gear shaft. For an advantageously, contact-free position determination of the gearshift fork, a magnet is provided as the position transmitter, while the sensor provided at a distance to the same or in the transmission housing is configured as a magnetic sensor. To attach or accommodate the magnet, a protrusion is envisaged on one of the two ends of the gearshift fork with the protrusion advantageously formed from the gearshift fork. The magnet is, in turn, accommodated in an element, which is attached on the protrusion. Since the sensor is accommodated in a separate housing, which is inserted in an opening of the transmission housing, inclinations in the transmission housing can be compensated for to allow the necessary horizontal orientation.
The disadvantages of the state of the art are that separate position transmitters and sensors must be provided on the shifting fork and/or the transmission housing to allow precise determination of the position of the sliding sleeve, requiring additional devices, which increases the number of components and thus the costs.
It is, therefore, the object of the invention to provide a method which allows precise determination of the position of a shifting element, for example of a motor vehicle, and eliminates the disadvantages of the state of the art.
The underlying goal of the invention is achieved with a method of this type for determining the position of a shifting element.